Apparatus for transferring articles between a conveyor and a stack

ABSTRACT

The conveyor is disposed on a predetermined level. The height of the stack is changed by the transfer of articles by said apparatus. Pivotal mounting means are vertically movably mounted on a frame and define a horizontal axis. A rocker arm assembly is pivoted to said mounting means on said axis for a rocking movement through substantially 180* and has an outer end which is remote from said pivotal axis. A gripper is carried by said rocker arm assembly at said outer end and adapted to hold articles. Vertical drive means are provided to adjust said pivotal axis in height during a rocking movement of said rocker arm assembly. Rocking drive means cooperate with said pivotal mounting means to impart to said rocker arm assembly a pivotal movement through 180*. connecting means are connected between said vertical drive means and said rocking drive means and serve to impart to said rocker arm assembly a rocking movement in dependence on the vertical movement of said pivotal mounting means. Means are provided to define a reference level which is spaced a predetermined vertical distance above said stack.

United States Patent [1 1 Bargstedt 1 Sept. 17, 1974 1 APPARATUS FORTRANSFERRING ARTICLES BETWEEN A CONVEYOR AND A STACK [76] Inventor: GerdBargstedt,Wischhafenersand 91, 2161 Drochtersen, Germany [22] Filed:June 13, 1972 [21] App]. N0.: 262,285

[30] Foreign Application Priority Data June 15, 1971 Germany 2129576[52] US. Cl 214/6 FS, 214/1 BV, 214/8.5 D [51] Int. Cl. B65g 57/04 [58]Field of Search 214/6 FS, 6 A, 6 P, 6 G, 214/6 DK, 309, 1 BD. 1 EV, 8.5C, 8.5 D, 8.5 H

[56] References Cited UNITED STATES PATENTS 2,832,478 4/1958 Malewicz etal. 214/1 BD 3,095,082 6/1963 Allgeyer 214/1 BD 3,178,041 4/1965 Wheat214/6 FS X 3,587,888 6/1971 Warren 214/1 BV 3,617,054 11/1971Schilling.... 214/1 BD 3,675,790 7/1972 Avril 214/6 G X PrimaryExaminerRobert J. Spar Attorney, Agent, or FirmToren, McGeady andStanger [57] ABSTRACT The conveyor is disposed on a predetermined level.The height of the stack is changed by the transfer of articles by saidapparatus. Pivotal mounting means are vertically movably mounted on aframe and define a horizontal axis. A rocker arm assembly is pivoted tosaid mounting means on said axis for a rocking movement throughsubstantially 180 and has an outer end which is remote from said pivotalaxis. A gripper is carried by said rocker arm assembly at said outer endand adapted to hold articles. Vertical drive means are provided toadjust said pivotal axis in height during a rocking movement of saidrocker arm assembly. Rocking drive means cooperate with said pivotalmounting means to impart to said rocker arm assembly a pivotal movementthrough 180. connecting means are connected between said vertical drivemeans and said rocking drive means and serve to impart to said rockerarm assembly a rocking movement in dependence on the vertical movementof said pivotal mounting means. Means are provided to define a referencelevel which is spaced a predetermined vertical distance above saidstack.

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PATENIEDSEH 7mm saw 09 HF 1o PATENTEDsEP 1 mm sum 10 0F 10 my. m

APPARATUS FOR TRANSFERRING ARTICLES BETWEEN A CONVEYOR AND A STACK Thisinvention relates to an apparatus for stacking or unstacking articles,which apparatus provides for a transfer of articles between a conveyordisposed on a predetermined level, and the top of a stack which changesih height, and which apparatus comprises a rocker arm assembly, which ispivotally movable through substantially 180 and which is movable inheight and at one end carries a gripper, and in which apparatus avertical drive cooperates with a rocking drive.

An application of the invention is found in the stacking of plates. Thegripper may consist, e.g., of vacuum cups.

A rocker arm assembly consists, e.g., of two parallel rocker arms,between which a cross-beam is provided, which carries the vacuum cups.That cross-beam is rotatably mounted and driven so that the vacuum cupsalways face downwardly.

In a known design disclosed in Opened German Application 1,907,763 thepivotal mounting means for the rocker arm assembly is repeatedly movedin height by a drive chain as far as to the upper reversing sprocket ofthe chain and the rocker arm assembly when it has reached its uppermostposition is pivotally moved through 180. This results in a sudden, highacceleration of the gripper at the outer end of the rocker arm assembly.

Regardless of the height of the conveyor or the top of the stack, therocker arm assembly is moved always to its uppermost position before itis pivotally moved and there is no vertical movement during the pivotalmovement. After the pivotal movement, the vertical movement in the othersense is continued by the oneway coupling to the drive chain.

That design has the disadvantage that the velocity of the pivotalmovement is suddenly increased and that it involves long and changingtimes of operation because the lifting and lowering movements along thestack take different times in dependence on the height of the stack.

it is an object of the invention to provide an apparatus which is of thekind stated above and which when used in conjunction with a stack placedon the floor and changing in height depending on the nature of itsprocessing ensures that the transfer path from the top of the stack tothe conveyor and vice versa is as short as possible.

This object is accomplished according to the invention in that the pivotbearings or the rocking shaft for the rocker arm assembly is adjustablein height during the rocking movement and the uppermost position of thepivot bearings or the rocking shaft is variable in dependence on achanging reference level above the stack. It will be of specialadvantage if the pivotal movement and the vertical movement begin andterminate substantially at the same time.

In the apparatus according to the invention the rocker arm assembly islifted only to the level which is required in view of the instantaneousheight of the stack so that excessive vertical movements are avoided.The speed of operation is further increased in that the verticalmovement and pivotal movement overlap in time. A high speed of operationis also enabled in that the velocity changes in accordance with a sinefunction resulting in a gradual acceleration to the highest speed and asubsequent deceleration. important features of the invention reside inthe coupling of the vertical drive with the drive means and in thevariability of the vertical drive. In practice, the change of thevertical drive results in a change of the are along which the gripper ispivotally moved and in a change of the length of the transfer paththereof so that the gripper actually travels only over the distancewhich is required in each case.

The vertical drive consists desirably of a crank member and the lengthof the crank member is variable in dependence on the height of thestack. As a result, the length of the crank member can be selected sothat the crank member when moving between two end positions determinesthe uppermost and lowermost positions of the rocker arm assembly. Theeffective length of the crank member is adjustable in dependence on thechange of the height of the stack.

The crank arm comprises suitably a screw or rack along which a nut orpinion, respectively, is movable. This nut or pinion is connected to adrive motor and provides an adjustable stop defining the effectivelength of the crank member.

In a preferred arrangement, the nut or pinion is provided with a chainsprocket, which is preferably freely rotatable and around which avertical drive chain is trained, one end of which is connected to avertically movable bearing plate for the rocker arm assembly whereas theother end of the chain is connected to that end of the crank memberwhich serves as a permanent point of reference for the change of thelength of the crank member. This permanent point of reference ensuresthat there will always be a fixed reference point for one end positionin dependence on the change in length of the crank member. This one endposition may be, e.g., the end position for the conveyor, which has acertain overall height. The other end position of the pivotal movementis adjusted in dependence on the changing height of the stack.

It is also preferred to provide the crank member in the form of a doublecrank, which extends from its axis 7 of rotation on both sides. Thisfeature enables the provision of a 1:2 transmission ratio regarding thespeed and the travel of the rocker arm assembly so that the machine canbe designed more economically. Besides, the mass distribution isimproved. The double crank has further advantages, which will beexplained hereinafter, in special applications.

In a desirable embodiment, the double crank carries at one end the drivemotor for a rotation of the screw and the chain is secured to that end.That end is the point of reference for the fixation of the drive chain.

In a particularly desirable embodiment the drive means consist of acrank mechanism and are arranged so that the rocker arm assembly is inone end position of its path of travel when a connecting rod and/or rackwhich is driven by the crank mechanism and operatively connected to theshaft of the rocker arm assembly is aligned with the crank. Thisarrangement will result in a change in speed according to a sinefunction resulting in an automatic deceleration or braking of themovement before each end position.

The crank mechanism is provided with a capstan head, to which the rackis linked. That feature will be adopted if predetermined largerdistances are to be traveled.

In an arrangement which comprises a frame having columns in whichbearing plates carrying the rocker arms are guided for verticalmovement, a particularly desirable feature resides in that the driveshaft for the crank mechanism and the crank member or double crank ofthe vertical drive extend vertically and are provided on a cross-memberbetween the vertical guides, and the bearing plates are provided with adrive chain for the crank member or double crank. The resultingarrangementis relatively light in weight and is economically composed ofseveral parts.

In a desirable embodiment, an abutment of the chain is adjustable at abearing plate to enable a selection of the reference height over theconveyor means. A handwheel may be provided for this adjustment. It isalso preferred to provide for an automatic adjustment of the adjustableabutment in step with the cyclic operation of the machine and for thispurpose to provide the adjustable abutment'in the form of a pneumatic orhydraulic actuator, which imparts to the gripper an initial or finalstroke when the rocker arms have reached their end positions. Inconjunction with the above-mentioned manual adjustment, the actuatorwould then be adjustable at the bearing plate in a vertical direction.

It is also pointed out that particularly desirable conditions will beobtained if a crank of the crank mechanism and the crank member ordouble crank of the vertical drive are parallel to each other. As aresult, the rocking drive and vertical drive are synchronized, as isessential for the invention.

The crank mechanisfn suitably drives a square shaft, which constitutes adrive element for a bevel gearing provided on the stub shaft of therocker arm assembly, and a drive gear is slidably mounted on the squareshaft. In such an arrangement, a torque-transmitting member comprisingfour rollers is preferably provided between the square shaft and ahousing for the driving bevel gear, which housing carries a stub shaftof the rocker arm assembly, and said four rollers roll on re spectiveside faces of the square shaft. This results in a particularlylow-friction driving connection.

In another embodiment the double crank is provided on a horizontal stubshaft and provided with a cam slot, and a sliding block guided in saidcam slot is connected by a pivoted rod to a vertically guided member,which is adjustable in height in dependence on the height of the stack.This arrangement is disclosed to show that the embodiments described andshown by way of example are not the only ways to carry out theinvention. For

the same reason it is pointed out that in'another suitable arrangementthe double crank non-rotatably secured to the rocker arm assembly isconnected by a linkage to a drive shaft on which the drive motor isprovided and the drive shaft is in mesh with a rack to change thedistance from the rocker arm assembly, the vertical drive beingconnected to a drive wheel in the double crank.

In another embodiment, the double crank comprises a rack, which mesheswith a pinion connected to a drive motor for changing the effectivelength of the double crank. This pinion meshes also with a rack which ispivoted to the frame.

In the described arrangement, the vertically movable rocker arm assemblyis provided with a counterweight, which is guided in the columns andconnected by a rope to at least one bearing plate of the rocker armassembly. This embodiment is characterized according to the invention inthat the rope is connected to the rocker arm assembly at a point whichis spaced from the pivot bearing thereof and exerts an opposing torqueso that the drive power is utilized in a particularly desirable manner.

The invention will now be explained with reference to embodiments shownby way of example in the drawing, in which FIG. 1 is a front elevationshowing an apparatus according to the invention,

FIG. 2 is a side elevation of FIG. 1,

FIG. 3 is a fragmentary top plan view showing the left-hand half of FIG.1,

FIG. 4 is a fragmentary top plan view showing the right-hand half ofFIG. 1,

FIG. 5 is a top plan view of FIG. 1, partly in a section taken on lineVV in FIG. 1, and shows only the parts intended to drive the rocker armassembly,

FIGS. 6 and 7 are enlarged fragmentary end views of FIG. 1,

FIGS. 8 to 8e are diagrammatic representations of the sequence of motionin another embodiment,

FIG. 9 is an enlarged view showing essential elements of the embodimentof FIG. 8, and

FIG. 10 is a diagrammatic side elevation showing the apparatus providedwith the elements of FIGS. 8 and 9.

A preferred embodiment is shown in FIGS. 1 to 7, wherein like parts aredesignated with like reference characters.

As is particularly apparent from FIGS. 1 and 2, two columns 3, 4 areprovided beside a support for a stack 2. This support consists of aroller conveyor 1. Bearing plates 5, 6 are vertically movably guided onthe columns 3, 4. The bearing plate 5 is provided, e.g., with the guiderollers 7, 8, 9, 10, which roll on different sides of a flange 11. Therollers 7, 8 are shown by way of example in FIG. 5.

The rollers 13, 14 of the bearing plate 6 roll on the correspondingflange 12 of column 4.

The columns are connected at the top by a crossbeam 15.

In the rocking drive means of the invention, the bearing plates 5, 6 areprovided with pivot bearings 16, 17 for the rocker arm assembly whichcomprises the rocker arms 18, 19, which are connected by a crossbeam 20carrying the vacuum cups 21, 22.

A parallel-holding shaft 23 is rotatably mounted in the bearing plates5, 6 and is provided at its ends with pinions 24, 25, which mesh withracks 26, 27 of the columns 3, 4. As a result, the two bearing plates 5,6 are constrained to move parallel to each other.

A stub shaft 28 extending through the pivot bearing 17 is rotatablymounted in a bevel gear housing 29 and connected to a bevel wheel 30,which meshes with a bevel wheel 31 in the housing 29. The bevel wheel 31is slidably and nonrotatably mounted on a square shaft 32, which isparallel to the column 4. The bevel wheel 31 is connected to atorquetransmitting member, which is generally designated 33 and by meansof a swivel member 34 is mounted on the housing 29 and imparts rotationto the bevel wheel 31 and the square shaft 32.

It is apparent from FIG. 5 that the torquetransmitting member 33comprises a capstan head, in which four rollers 35, 36, 37, 38 arerotatably mounted, which roll on the sides of the square shaft 32 sothat the rotational adjustment of the square shaft is transmitted to thebevel wheel 31 with relatively low friction. The square shaft 32 isrotatably suspended at its upper end in an end journal bearing 39 on thecross-beam and carries a pinion 40 in mesh with a rack 41 (see also FIG.4), which is held in mesh by means of a backing roller 42. The rackitself is pivoted on a pivot pin 43 in a capstan head 44, which isslidably guided on the cross-beam 15.

A cranked connecting rod 45 is also connected to the pivot pin 43 and isrotatably mounted on the pin 46 of a crank 47. By means of thereversible drive motor 48 and a rope or chain 49 trained around a ropepulley or chain sprocket 50 the crank 47 is pivotally movable throughsteps of 180 along an arc of a circle 51 shown in FIG. 3.

Together with the crank 47, the vertical drive means of the inventionare shown to include a double crank generally designated 53 which ismounted on the same drive shaft 52 carrying the sprocket 50. The doublecrank extends, e.g., equal distances from the drive shaft 52 on bothsides. In the embodiment shown by way of example, a screw 55 isrotatably mounted in the double crank and connected to a gearmotor 56,which is operated in dependence on the height of the stack to move atraveling nut 57 from the opposite end 58 as the stack decreases inheight. A chain sprocket 59 is freely rotatably mounted on the travelingnut beside an element 60 for guiding the chain to ensure a constantengagement. During a pivotal movement of the crank through 180", the enddesignated 58 moves along the arc of a circle 61. The chain sprocket 59may be displaced beyond the shaft 52 to that end of the double crank atwhich the gearmotor 56 is disposed. The drive chain 62 is trained aroundthe chain sprocket 59 and is secured at 63 to that end toward which thechain sprocket 59 is moved. As a result, a fixed reference level overthe conveyor 64 (FIG. 2) is provided for the vertical adjustment of therocker arms. It should be taken into account that this referenceposition is established in that the end provided with the fixing means63 is pivotally moved outwardly relative to the cross-beam whereas thedouble crank 53 is aligned with the cross-beam. A closer approach of thefixing means 63 to the other abutment of the chain 105 is not possible.

It is apparent that the gearmotor 56 is connected by a chain drive 65 tothe screw 55.

The use of the double crank with the chain sprocket 59 affords theadvantage that a 1:2 transmission ratio is obtained for the movement andspeed.

The chain 62 is guided in the capstan head by two guide sprockets 66, 67to extend to a chain sprocket 68 disposed adjacent to the column 4. Anintermediate chain fastener 69 is provided in an intermediate positionand changes the orientation of the chain for meshing through 90 inaccordance with the orientation of the guide sprocket 66, 67 and of thechain sprocket 68. The chain end 105 guided over the chain sprocket 68is secured to an abutment, which in accordance with FIGS. 1 and 2consists of an end portion of the piston rod 70 of a cylinder-pistonunit 71, which is mounted in the bearing bracket 6. The cylinder-pistonunit 71 is vertically adjustable along guide rods 72, 73 by means of ascrew 74 and a handwheel 75. The height of the support provided by thecross-beam can be adjusted in the directions of the double arrow 76 inFIG. 2 in dependence on the vertical adjustment. This adjustment couldalso be effected by a corresponding vertical adjustment of a hooklikeabutment. The cylinder-piston unit 71 also cooperates with a controlmeans not shown in detail in such a manner that the last approximately50 millimeters of the vertical movement are added in each end positionto the movement of the rocker arm assembly so that a careful handling isenabled.

In the embodiment described thus far, the crossbeam 20 and the vacuumcups 77 can move along the dotted line 78 so that the vacuum cups areraised only to the extent required to lift a top plate from the stack 2and as a result of the simultaneous displacement of the bearing plates5, 6 are then moved downwardly and laterally and thereafter downwardlybeyond the center of the top of the conveyor 64. This matching of themovements is accomplished in that the double crank 53 has the same driveimparted to it as the crank 47 for the pivotal movement of the rockerarms. The gearmotor 56 can be controlled by stack height sensing meanssuch as photoelectric means 56a for detecting the height of the stackor, alternatively by a step-by-step switch, the steps of whichcorrespond to the height of individual articles of the stack 2.

The motion curve 78 indicates that the transfer is effected along a pathwhich is as short as possible.

As is apparent from FIG. 5, a drive chain 79 is connected between therocking shaft and the cross-beam 20, which carries the vacuum cups 21,22 and which is rotatably mounted in the rocker arms 18, 19. The drivechain 79 is trained around a chain sprocket 80 nonrotatably connected tothe cross-beam 20 and at its other end is trained around a chainsprocket 81 fixed to the gearbox 29.

In this connection it is also pointed out that the connecting-rod 45 hasan offset portion 82 so that it will not strike on the drive shaft 52when an end position is assumed in which the crank member 47 is alignedwith the cross-beam 15.

A counterweight 88 is guided by means of the rollers 84, 85 and thebacking members 86, 87 on a flange 83 of the column 3 and is suspendedfrom a rope 89, which is trained around deflecting pulleys 90, 91, 92and connected to an abutment 93 in the intermediate portion of therocker arms 18, 19. Because the abutment 93 is spaced from the pivotpins of the rocker arms, which pivot pins extend through the pivotbearings 16, 17, the counterweight 88 exerts a moment on the rocker armassembly. That moment changes with the angle of the rocker arms relativeto the vertical so that a relatively exact balancing of the forcesacting on the loaded rocker arms can be accomplished.

Another embodiment is diagrammatically indicated in FIGS. 8 and 9. Inthe diagrammatically shown end view, the rocker arm assembly isdesignated 94 and shown in various positions. In this embodiment, thisrocker arm assembly is provided with a counterweight. The cross-beamcarrying the vacuum cups is designated 95 and cooperates with a conveyor96 having a constant height and a stack 97 having a changing height. Inthis embodiment, a double crank 99 is non-rotatably connected to thepivot bearing or the horizontal rocking shaft 98 of the rocker armassembly 94 and a pinion 101 is mounted at the end of the rocker armassembly 94 and in mesh with a rack 100. The pinion 101 is connected toa drive motor 102, to which it may be coupled by a worm gearing or bevelgearing, if desired. The pinion 101 is also in mesh with a rack 103,which is pivoted on an axis 104 to a column of the frame. Thus, arotation of the pinion 101 will change its relation to the rack 103 andto the rack 100 of the double crank 99, so that the latter will be swungout and its effective length relative to the rocking shaft 98 will bechanged. This effect is the same as that described with reference to thedouble crank 53 shown in FIGS. 1 to 5. This embodiment is described onlyto show that other arrangements may also be used.

FIG. 10 shows an embodiment comprising a rack 103, a pivot bearing 104and a gearmotor 102. In the embodiment of FIG. 10, the vertical drive iseffected in dependence on the rotation of the rocking shaft 98, which isdriven by a crank mechanism whereas the gearmotor 102 is controlled independence on the changing height of the stack.

The control is particularly accomplished with limit switches. Two limitswitches are associated with the rocker arms to define the positionsover the stack and the conveyor. Two additional limit switches areassociated with the bearing plates and the so-called double crank todefine the upper and lower end positions. The cylinder-piston unitforming an abutment for the drive chain of the vertical drive isprovided with another limit switch. To indicate that they are ready toreceive an article, e.g., at vacuum cups, the grippers are provided forthe stack 2 to indicate the presence of a stack. Additional limitswitches serve to detect the condition of the conveyor.

The limit switches control the described motors and also control thevacuum pump for the vacuum cups to operate in the required sequence.Such control systems can readily be designed in view of the describedsequence of motion of the mechanical system. It is pointed out that thedrive motor for the vertical adjustment and for operating the rocker armassembly is a reversible motor, just as the lift-setting motor providedon the double crank for adjustment to the stacking or unstackingoperation.

What is claimed is:

1. Apparatus for transferring articles between a conveyor disposed on apredetermined level and a stack of articles in order to change theheight of said stack, said appraratus comprising a frame, pivotalmounting means vertically movably mounted on said frame and defining ahorizontal pivotal axis, a rocker arm assembly pivotally mounted to saidmounting means on said axis for rocking movement through substantially180 and having an outer end remote from said pivotal axis, a grippercarried by said rocker arm assembly at said outer end and adapted tohold articles, vertical drive means for reciprocally adjusting thevertical height of said pivotal axis during rocking movement of saidrocker arm assembly, rocking drive means cooperating with said pivotalmounting means to impart to said rocker arm assembly pivotal movementthrough 180, connecting means arranged between said vertical drive meansand said rocking drive means to impart to said rocker arm assembly arocking movement in dependence upon the vertical reciprocal movement ofsaid pivotal mounting means, means for sensing the height of said stack,and means associated with said vertical drive means for determining inresponse to said stack height sensing means the uppermost position ofsaid pivotal mounting means at a level relative to the height of saidstack, said vertical drive means and said rocking drive means beingoperatively positioned in a superposed arrangement relative to eachother in such a manner that, as a result of said superposed arrangement,the vertical positioning of said pivotal axis is adjusted simultaneouslyduring rocking movement of said rocker arm assembly with the verticallocation of said pivotal axis being varied as a function of the sensedstack height.

2. Apparatus according to claim 1 wherein said vertical drive meanscomprise a crank member and a rectilinear drive mechanism including anelongated first drive element and a second drive element operativelyconnected to and movable along said first drive element, said crankmember having a variable effective length one end of which is defined bysaid second drive element, and a drive motor connected to said firstdrive element and operable to move said second drive element along saidfirst drive element.

3. Apparatus as set forth in claim 2, in which said first drive elementcomprises a screw and said second drive element comprises a nut threadedon said screw.

4. Apparatus as set forth in claim 2, in which said first drive elementcomprises a rack and said second drive element comprises a pinion inmesh with said rack.

5. Apparatus as set forth in claim 2, which comprises a freely rotatablechain sprocket connected to the second drive element, and

a chain trained around said chain sprocket,

one end of said chain'being connected to said pivotal mounting means,

the other end of said chain being connected to said second end of saidcrank member.

6. Apparatus as set forth in claim 5, in which said crank memberconsists of a double crank,

a pivot pin is mounted in the frame,

said crank member is mounted on said pivot pin and consists of a doublecrank extending on both sides of said pivot pin,

a drive motor for driving said drive mechanism is carried by said crankmember at one end, and

said chain is connected to the same end of said crank member.

7. Apparatus as set forth in claim 6, in which a square shaft isprovided, which is operatively connected to said crank mechanism,

said pivotal mounting means comprise a stub shaft which is rotatable torock said rocker arm assemy.

a bevel gearing is interconnected between said square shaft and saidstub shaft and comprises an input bevel wheel, which is slidably mountedon said square shaft,

said input bevel wheel is mounted in a housing, which carries said stubshaft, and

a torque-transmitting member is connected between said square shaft andsaid housing and carries four rollers adapted to roll on respectivesides of said square shaft.

8. Apparatus as set forth in claim 6, in which said frame carries ahorizontal stub shaft,

said double crank is mounted on said stub shaft and carries a cam slot,

a slide block is guided in said cam slot,

a constraining member is vertically guided on said frame,

a rod is connected to said slide block and pivoted to said constrainingmember and said vertical drive means are connected to said constrainingmember and operable to adjust the same in a vertical direction.

9. Apparatus as set forth in claim 6, in which said double crank isprovided with a rack,

a pinion is in mesh with said rack,

a drive motor is connected to said pinion to move the same along saidrack in order to change the effective length of said double crank, and

a second rack is pivoted to said frame and in mesh with said pinion.

10. Apparatus as set forth in claim 1, in which said rocking drive meanscomprise a crank mechanism mounted in said frame and a drive shaft forsaid crank mechanism,

said drive shaft and said crank of said vertical drive means extendvertically,

said frame comprises vertical guides,

a cross-member is guided on said vertical guides and carries said driveshaft and said crank member,

a chain is connected to said crank member and operable to drive the sameand connected to said pivotal mounting means, and

said pivotal mounting means comprise a rocking shaft which is rotatableto rock said rocker arm assembly,

a rod is connected to said rocking shaft and operable by said crankmechanism to rotate said rocking shaft, and

said crank mechanism is arranged so that said rocker arm assembly is inone end position of its rocking movement when said rod is aligned withsaid crank member.

11. Apparatus as set forth in claim 10, in which said crank mechanismcomprises a capstan head and said rod consists of a rack which ispivoted to said capstan head.

12. Apparatus as set forth in claim 10, in which said chain is connectedto an abutment,

said pivotal mounting means comprise a bearing plate vertically movablymounted on said frame, and

said abutment is adjustably mounted on said bearing plate for aselection of the reference height over said conveyor.

13. Apparatus as set forth in claim 12, which comprises an adjustingmeans connected between said frame and said abutment, and

means for intermittently adjusting said adjusting means in step with themovement of said rocker arm assembly,

said adjusting means being arranged to impart to said gripper initialand final strokes, respectively, when said rocker arm assembly reachesits two end positions.

14. Apparatus as set forth in claim 10, in which said crank mechanismcomprises a crank which is parallel to the crank member of said verticaldrive means.

15. Apparatus as set forth in claim 1, in which a rope pulley is mountedin an upper portion of said frame,

a rope is trained around said rope pulley and on one side of said pulleyis connected to said vertically movable rocker arm assembly at a pointdisposed between said gripper and said pivotal axis and spaced from thelatter, and

a counterweight is connected to said rope on the other side of saidpulley to exert by means of said rope an opposing moment on said rockerarm assembly.

1. Apparatus for transferring articles between a conveyor disposed on apredetermined level and a stack of articles in order to change theheight of said stack, said appraratus comprising a frame, pivotalmounting means vertically movably mounted on said frame and defining ahorizontal pivotal axis, a rocker arm assembly pivotally mounted to saidmounting means on said axis for rocking movement through substantially180* and having an outer end remote from said pivotal axis, a grippercarried by said rocker arm assembly at said outer end and adapted tohold articles, vertical drive means for reciprocally adjusting thevertical height of said pivotal axis during rocking movement of saidrocker arm assembly, rocking drive means cooperating with said pivotalmounting means to impart to said rocker arm assembly pivotal movementthrough 180*, connecting means arranged between said vertical drivemeans and said rocking drive means to impart to said rocker arm assemblya rocking movement in dependence upon the vertical reciprocal movementof said pivotal mounting means, means for sensing the height of saidstack, and means associated with said vertical drive means fordetermining in response to said stack height sensing means the uppermostposition of said pivotal mounting means at a level relative to theheight of said stack, said vertical drive means and said rocking drivemeans being operatively positioned in a superposed arrangement relativeto each other in such a manner that, as a result of said superposedarrangement, the vertical positioning of said pivotal axis is adjustedsimultaneously during rocking movement of said rocker arm assembly withthe vertical location of said pivotal axis being varied as a function ofthe sensed stack height.
 2. Apparatus according to claim 1 wherein saidvertical drive means comprise a crank member and a rectilinear drivemechanism including an elongated first drive element and a second driveelement operatively connected to and movable along said first driveelement, said crank member having a variable effective length one end ofwhich is defined by said second drive element, and a drive motorconnected to said first drive element and operable to move said seconddrive element along said first drive element.
 3. Apparatus as set forthin claim 2, in which said first drive element comprises a screw and saidsecond drive element comprises a nut threaded on said screw. 4.Apparatus as set forth in claim 2, in which said first drive elementcomprises a rack and said second drive element comprises a pinion inmesh with said rack.
 5. Apparatus as set forth in claim 2, whichcomprises a freely rotatable chain sprocket connected to the seconddrive element, and a chain trained around said chain sprocket, one endof said chain being connected to said pivotal mounting means, the otherend of said chain being connected to said second end of said crankmember.
 6. Apparatus as set forth in claim 5, in which said crank memberconsists of a double crank, a pivot pin is mounted in the frame, saidcrank member is mounted on said pivot pin and consists of a double crankextending on both sides of said pivot pin, a drive motor for drivingsaid drive mechanism is carried by said crank member at one end, andsaid chain is connected to the same end of said crank member. 7.Apparatus as set forth in claim 6, in which a square shaft is provided,which is operatively connected to said crank mechanism, said pivotalmounting means comprise a stub shaft which is rotatable to rock saidrocker arm assembly, a bevel gearing is interconnected between saidsquare shaft and said stub shaft and comprises an input bevel wheel,which is slidably mounted on said square shaft, said input bevel wheelis mounted in a housing, which cArries said stub shaft, and atorque-transmitting member is connected between said square shaft andsaid housing and carries four rollers adapted to roll on respectivesides of said square shaft.
 8. Apparatus as set forth in claim 6, inwhich said frame carries a horizontal stub shaft, said double crank ismounted on said stub shaft and carries a cam slot, a slide block isguided in said cam slot, a constraining member is vertically guided onsaid frame, a rod is connected to said slide block and pivoted to saidconstraining member and said vertical drive means are connected to saidconstraining member and operable to adjust the same in a verticaldirection.
 9. Apparatus as set forth in claim 6, in which said doublecrank is provided with a rack, a pinion is in mesh with said rack, adrive motor is connected to said pinion to move the same along said rackin order to change the effective length of said double crank, and asecond rack is pivoted to said frame and in mesh with said pinion. 10.Apparatus as set forth in claim 1, in which said rocking drive meanscomprise a crank mechanism mounted in said frame and a drive shaft forsaid crank mechanism, said drive shaft and said crank of said verticaldrive means extend vertically, said frame comprises vertical guides, across-member is guided on said vertical guides and carries said driveshaft and said crank member, a chain is connected to said crank memberand operable to drive the same and connected to said pivotal mountingmeans, and said pivotal mounting means comprise a rocking shaft which isrotatable to rock said rocker arm assembly, a rod is connected to saidrocking shaft and operable by said crank mechanism to rotate saidrocking shaft, and said crank mechanism is arranged so that said rockerarm assembly is in one end position of its rocking movement when saidrod is aligned with said crank member.
 11. Apparatus as set forth inclaim 10, in which said crank mechanism comprises a capstan head andsaid rod consists of a rack which is pivoted to said capstan head. 12.Apparatus as set forth in claim 10, in which said chain is connected toan abutment, said pivotal mounting means comprise a bearing platevertically movably mounted on said frame, and said abutment isadjustably mounted on said bearing plate for a selection of thereference height over said conveyor.
 13. Apparatus as set forth in claim12, which comprises an adjusting means connected between said frame andsaid abutment, and means for intermittently adjusting said adjustingmeans in step with the movement of said rocker arm assembly, saidadjusting means being arranged to impart to said gripper initial andfinal strokes, respectively, when said rocker arm assembly reaches itstwo end positions.
 14. Apparatus as set forth in claim 10, in which saidcrank mechanism comprises a crank which is parallel to the crank memberof said vertical drive means.
 15. Apparatus as set forth in claim 1, inwhich a rope pulley is mounted in an upper portion of said frame, a ropeis trained around said rope pulley and on one side of said pulley isconnected to said vertically movable rocker arm assembly at a pointdisposed between said gripper and said pivotal axis and spaced from thelatter, and a counterweight is connected to said rope on the other sideof said pulley to exert by means of said rope an opposing moment on saidrocker arm assembly.